/* 
 * ------------------------------------------------------------------------
 *  Copyright by KNIME AG, Zurich, Switzerland
 *  Website: http://www.knime.com; Email: contact@knime.com
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License, Version 3, as
 *  published by the Free Software Foundation.
 *
 *  This program is distributed in the hope that it will be useful, but
 *  WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, see <http://www.gnu.org/licenses>.
 *
 *  Additional permission under GNU GPL version 3 section 7:
 *
 *  KNIME interoperates with ECLIPSE solely via ECLIPSE's plug-in APIs.
 *  Hence, KNIME and ECLIPSE are both independent programs and are not
 *  derived from each other. Should, however, the interpretation of the
 *  GNU GPL Version 3 ("License") under any applicable laws result in
 *  KNIME and ECLIPSE being a combined program, KNIME AG herewith grants
 *  you the additional permission to use and propagate KNIME together with
 *  ECLIPSE with only the license terms in place for ECLIPSE applying to
 *  ECLIPSE and the GNU GPL Version 3 applying for KNIME, provided the
 *  license terms of ECLIPSE themselves allow for the respective use and
 *  propagation of ECLIPSE together with KNIME.
 *
 *  Additional permission relating to nodes for KNIME that extend the Node
 *  Extension (and in particular that are based on subclasses of NodeModel,
 *  NodeDialog, and NodeView) and that only interoperate with KNIME through
 *  standard APIs ("Nodes"):
 *  Nodes are deemed to be separate and independent programs and to not be
 *  covered works.  Notwithstanding anything to the contrary in the
 *  License, the License does not apply to Nodes, you are not required to
 *  license Nodes under the License, and you are granted a license to
 *  prepare and propagate Nodes, in each case even if such Nodes are
 *  propagated with or for interoperation with KNIME.  The owner of a Node
 *  may freely choose the license terms applicable to such Node, including
 *  when such Node is propagated with or for interoperation with KNIME.
 * -------------------------------------------------------------------
 * 
 * History
 *   Nov 23, 2005 (wiswedel): created
 *   21.06.06 (bw & po): reviewed
 */
package org.knime.core.data.def;

import java.util.Iterator;
import java.util.NoSuchElementException;

import org.knime.core.data.DataCell;
import org.knime.core.data.DataRow;

/**
 * Default implementation of an iterator over the <code>DataCell</code>s of a
 * DataRow. It uses the <code>getNumCells()</code> and
 * <code>getCell(int)</code> methods of the underlying row to return the
 * cells. Hence, it starts at the cell of the column with index 0 and then
 * sequentially returns the cells up to the last cell (of the column with the
 * highest index) in the row.
 * <p>
 * The iterator doesn't support removal of datacells, an invocation of the
 * method <code>remove()</code> will end up with an exception.
 * 
 * @author wiswedel, University of Konstanz
 */
public class DefaultCellIterator implements Iterator<DataCell> {

    /** The row to iterate over. */
    private final DataRow m_row;

    /** The index of the cell that will be returned next. */
    private int m_index;

    /**
     * Creates a new iterator over a given <code>DataRow</code>.
     * 
     * @param row The row to traverse.
     * @throws NullPointerException If the argument is null.
     */
    public DefaultCellIterator(final DataRow row) {
        if (row == null) {
            throw new NullPointerException("Row must not be null.");
        }
        m_row = row;
        m_index = 0;
    }

    /**
     * {@inheritDoc}
     */
    public boolean hasNext() {
        return m_index < m_row.getNumCells();
    }

    /**
     * {@inheritDoc}
     */
    public DataCell next() {
        if (!hasNext()) {
            throw new NoSuchElementException("Iterator is at end.");
        }
        DataCell result = m_row.getCell(m_index);
        m_index++;
        return result;
    }

    /**
     * Throws {@link UnsupportedOperationException} as removal of datacells from
     * a row is not permitted.
     * 
     * @see java.util.Iterator#remove()
     */
    public void remove() {
        throw new UnsupportedOperationException(
                "Removing cells is not allowed.");
    }

}
